2020 CSAT, all questions
UPSC Prelims 2020 · CSAT
Question 59: Basic Numeracy
In a class, there are three groups A, B and C. If one student from group A and two students from group B are shifted to group C, then what happens to the average weight of the students of the class?
aIt increases.
bIt decreases.
cIt remains the same.
dNo conclusion can be drawn due to insufficient data.
AnswerUPSC’s answer is (c).
The students who move from groups A and B go to group C, but all of them are still in the class. The total weight and the number of students in the class do not change, so the class average is unchanged. Each group's average may change, but the whole class's average cannot.
Why each option is right or wrong
- (a) Total weight and head count are the same, so the average cannot rise.
- (b) For the same reason, it cannot fall.
- (c) Right: no student leaves the class, so the class average is unchanged.
- (d) No data on individual weights is needed.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2020, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.